Skin, soft tissue & bone infections Flashcards
What is cellulitis and what is it caused by?
Cellulitis is a skin and superficial soft tissue infection which is usually caused by Staph Aureus (commonly found on the skin)/ other Strep (will go in if there is a cut/immunosuppressed/diabetes). Bacteria commonly enter into the infectious site via an existing wound (e.g. abscess/ ulcer/skin break/bite)
- Will become red, hot and swollen
What is this condition?
Cellulitis
(red, hot & swollen)
What are the clinical features (signs & symptoms) of someone with cellulitis?
Signs
- High temp
- Unilateral
- Swelling
- Hot to touch
- Well demarcated (draw a line around area → measure if getting worse or better)
Symptoms
- Fever
- Pain → proportional to severity of the presentation
- Loss of function
What are the risk factors of someone with cellulitis?
- Reduced sensation (e.g. Diabetic Neuropathy)
- Reduced circulation (e.g. Congestive Cardiac Failure).
What investigations would you do to someone with cellulitis?
-
Bedside
- Observations (NEWS score - ?severity of infection).
- Wound Swabs (then start empirical treatment)+ Cultures (ideally before antibiotics → to check if infection has got into blood stream → IV or topical or PO).
-
Bloods
- FBC (assess inflammatory response).
- CRP (assess inflammatory response)
- +/- blood cultures if unwell.
-
Imaging
- Consider Doppler Ultrasound Scan (to rule out DVT)
- Consider MRI (able to see if osteomyelitis) Imaging
What is the management of someone with cellulitis?
-
Conservative (obs, pain relief, risk factor management)
- Border Marking
(assess treatment efficacy/infective spread).
- Border Marking
-
Medical
- IV/PO Antibiotics (in severe infection).
- Flucloxacillin usually first line.
- (+/- Surgical)
- Potential for debridement if severe/spreading despite treatment.
- Amputation → if spreading and resistant → spread into bone/+ tissue
- OR able to just remove infected tissue
What is the differential diagnosis of cellulitis?
- Necrotising fasciitis
- Chronic venous changes
-
Deep vein thrombosis
*
What is necrotising fasciitis (causes, clinical features, diagnosis, management & investigations)?
What it is & what causes it?
- This is a severe soft tissue infection caused by Group A Strep (Strep Pyogenes).
- Release of toxins by S. Pyogenes exacerbates extent of tissue damage by the infection (can lead to Septic Shock/Toxic Shock Syndrome.) → Tissue necrosis at the infected site also allows dissemination of infective material into the blood stream and cause a Systemic Response.
Clinical features
- This presents with a hot, red, swollen area of skin with necrotic tissue and SEVERE PAIN (pain extends further than rash).
- Poorly demarcated edges with areas of purple/black tissue (necrosis).
DIAGNOSIS:
- Skin swabs which are sent for MC&S.
MANAGEMENT:
- Medical: Broad Spectrum IV Antibiotics, Analgesia, IV Fluid. (as LOW BP)
- Surgical debridement to prevent spread of infection (need a margin clear of infection) +/- amputation.
Investigations
- Bedside: Observations, Wound Swab.
- Bloods: FBC, U&Es, CRP, Blood Cultures (high risk of septicaemia), Lactate (tissue necrosis). Likely ABGs/VBGs.
- Imaging: USS Leg (?gas gangrene within the tissue).
What is this condition?
Necrotising Fasciitis
How could we differentiate necrotising fasciitis clinically from cellulitis?
- Pain is disproportionate to the area of infection in NF (pain is much wider spread than the area of visible infection).
- Areas of necrosis are seen in NF (not usually seen in cellulitis).
- Poorly demarcated edges in NF (usually relatively clear borders in cellulitis).
- Patient are usually much more unwell with necrotising fasciitis.
- HIGH NEWS score in NF
What is chronic venous changes (common name for it, and mechanism of how it happens)
- Lipodermatosclerosis (inverted champagne appearance) results from chronic inflammation and fibrosis of the dermis and subcutaneous tissue of the lower legs. This is characterized by painful inflammation above the ankles, which may be mistaken for cellulitis or phlebitis. Chronic venous insufficiency leads to oedema and hemosiderin deposition (causes brown discolouration of the legs), and deposition of other waste substances → Venous insufficiency prevents waste substances and fluid flowing from the lower limbs back to the central circulatory system. It therefore leaks out into the tissues of the lower limbs and causes discolouration***, ***swelling*** and ***inflammation.
What is this condition?
Chronic Venous Changes → Lipodermatosclerosis
How could we differentiate Chronic Venous Changes (Lipodermatosclerosis)clinically fromcellulitis?
- Not hot to touch, usually not painful, almost always BILATERAL
What is this condition?
Deep Vein Thrombosis
What is a DVT (risk factors, relevent
Deep Vein Thrombosis presents with a red, swollen UNILATERAL lower limb. DVT within a blood vessel causes thrombophlebitis which causes calf tenderness. May also present with low grade pyrexia. Thrombus is usually within the Femoral/Popliteal vein.
Risk factors for DVT include: immobilisation, malignancy, pregnancy, COCP/HRT, clotting disorders, surgery.
Relevant Investigations:
Doppler Ultrasound imaging
D-Dimer → sensitive but includes INFLAMMATION & ClOT
WELL’S Score → do before D-dimer
How could we differentiate DVT clinically from cellulitis?
DVT → not hot to touch, well demarcated, risk factors, history
- Lower limb would be hot to touch in cellulitis, but less likely so in DVT.
- Note: Low grade pyrexia can develop in DVT due to inflammatory response caused by blood clot.
- Also take into account the difference in clinical risk factors – a patient who presents with a discharging wound and surrounding redness most likely has cellulitis, a patient who presents with a spontaneously red and swollen leg three days after a hip replacement most likely has a DVT.
What is this condition?
Osteomyelitis
What is osteomyelitis? (common causative organisms, risk factors)
Osteomyelitis is an infection of the bone. Most cases are acute and bacterial in origin, however patients can develop chronic osteomyelitis (able to see on X-ray)if the infection does not fully resolve.
Common causative organisms
- S. aureus (most common), Streptococci,Enterobacter spp., H. Influnzae, P.aeruginosa (especially in intravenous drug users).
Risk factors for developing osteomyelitis:
- Diabetes Mellitus
- Immunosuppression (long term steroids/AIDS).
- Alcohol excess.
- Intravenous drug use.
What are the clinical features of osteomyelitis?
-
Severe, constant pain* in the affected region.
- In patients with diabetic foot, pain may be absent due to peripheral neuropathy.
- Loss of function (e.g. unable to weight bear, unable to pick things up).
- On examination, the site will be tender. There may be overlying swelling and erythema.
- Pyrexia.
What is the link between osteomyelitis and diabetic foot?
What are the common sites of osteomyelitis?
- In adults, the vertebrae are the most commonly affected bones.
- Great Hallux is also commonly affected.
What is the cause of osteomyelitis?
Osteomyelitis can be caused by haematogenous spread (bacteraemia disseminates from elsewhere via the blood stream), direct inoculation of micro-organisms into the bone (such as following an open fracture or penetrating injury), or direct spread from nearby infection (such as cellulitis).
What is Potts disease?
What are the investigations and management of osteomyelitis?
Investigations
Bedside - Observations (fever, ?septic), Wound swabs.
Blood test - FBC, CRP, U&Es, Blood cultures (positive in around 60% cases)
Imaging - Plain film → severe (X-rays, MRI → if acute (Definitive diagnosis).
- Gold Standard = bone biopsy at debridement → >90% sensitivity Management
Medical - Long Term IV Antibiotics (4-6 weeks).
Tailored to culture results if available
Surgical - If the patient clinically deteriorates, the limb shows evidence of deterioration, or imaging shows progressive bone destruction, then surgical management may be required to prevent chronic osteomyelitis developing.
